No investigation for over a month

I discovered last month that I was being billed for my drifta by DSTV even though I had not used this for almost 5 years and was sure that I had cancelled it. When I called DSTV regarding this they stated that they will investigate and come back to me. A month later after after not hearing anything from DSTV I called them to ask what's happening. After much investigation by the call centre agent it was revealed that the previous call centre agent had not initiated any investigation or inquiry and in fact nothing had been done or was in the process of being done. In fact had I not phoned then nothing would have been done at all. All that the call centre agent could advise was that they would start an investigation. I indicated that at this stage that was unacceptable. Why must I phone and chase DSTV when they dont do what they say they must do. Eventually spoke to a supervisor on Friday who PROMISED me they would get back to me that day. Surprise surprise by today they had not called me back. After much chasing I got hold of the supervisor who apologies and now indicated that they will try and initiate an investigation. Seriously at this stage the opportunity for investigations are over. Your service is a disgrace and you should be embarrassed about how you treat your customers. Not holding my breath on any actual feedback except for the we are investigating ******* that get peddled to me. Could you please explain why I must always chase....